Partner login

Questions about data format

Discusss here aspects related to the challenge dataset format, or link to tools, scripts, to assist in the data access.

DATA FORMATQ: I noticed that across the different datasets from all the subjects (both ADL and DRILL) there are plenty of portions where huge chunks of sensor data (mainly the accelerometers on the upper limbs) are missing, i.e. those columns contain NaNs. What happened there?A: NaN values correspond to missing samples in the wireless sensors. These are Bluetooth accelerometers that suffered a few disconnections with loss of data chunks (we had too many wireless things around).

LABELS

Q: Would you please explain the meaning of a zero value in either of the last two columns? Would it mean that there is no annotation available for the sensor instance?A: Exactly, a zero in the last columns means that no label is available for that particular sample (each row is a sample, with 30Hz rate). You can consider it like a "null class".
Concerning the posture/locomotion there are zeros mainly in transition phases, for example when the subject was first standing and then sitting down, you will see a label for standing, then a few zeros and finally a label for sitting. This is to avoid introducing samples which would not be representative of the activity. Regarding the gesture labels, there you have zeros whenever the corresponding gesture is not among the ones listed in the challenge description.

Hi,
After downloading the reissued dataset I've noticed that the first row of S1-Drill.dat has only 115 columns instead of 116 as described in the label column names. Comparing to the other .dat files I'm guessing that the first timestamp: 0 is missing.

how are oriented the devices placed on the body of the users? i mean, what is the reference coordinate system for the 3 sensors of every device (acc,gyro and magneto) with respect to the body of the user?

Q: Is it possible to have the datasheet of the gyros of the motion jacket? I need to calibrate the values they provide and your txt file just says that they output a raw value multiplied by 1000. I need to convert it to rad/s.

The IMUs are the xsens MTx sensors (datasheets available on request). No special processing is done on the rotation data, except from the fact that we multiplied the data by the factor indicated in the text file to have only integers instead of floats in the challenge file.
The datasheets can also be found in the attachments of this page.

Newsletter

The information on this website does not represent the opinion of the European Community, and is provided "as is". No guarantee or warranty is given that the information is fit for any particular purpose. The user uses the information at its sole risk and liability.